Document pQGr7qEa04dBYYDrEyn1D51j

Brogan & Partners Landfill Disposal Systems Author(s): Karen M. Slimak Source: Environmental Health Perspectives, Vol. 27 (Dec., 1978), pp. 309-316 Published by: Brogan & Partners Stable URL: http://www.jstor.org/stable/3428892 Accessed: 05/10/2009 18:42 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=brogpart. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. 1 Brogan & Partners is collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives. STOR http://www.jstor.org Environmental Health Perspectives Vol. 27, pp. 309-316, 1978 Landfill Disposal Systems by Karen M. Slimak The current status of landfill disposal of hazardous wastes in the United States is indicated by present ing descriptions of six operating landfills. These landfills illustrate the variety of techniques that exist in landfill disposal of hazardous wastes. Although some landfills more effectively isolate hazardous waste than others, all landfills must deal with the following problems. Leachate from hazardous waste landfills is generally highly polluted. Most landfills attempt to contain leachate at the site and prevent its discharge to surface or groundwaters. To retain leachate within a disposal area, subsurface barriers of materials such as concrete, asphalt, butyl rubber, vinyl, and clay are used. It is difficult to assure that these materials can seal a landfill indefinitely. When a subsurface barrier fails, the leachate enters the ground water in a concentrated, narrow band which may bypass monitoring wells. Once a subsurface barrier has failed, repairs are time-consuming and costly, since the waste above the repair site may have to be removed. The central problem in landfill disposal is leachate control. Recent emphasis has been on developing subsurface barriers to contain the wastes and any leachate. Future emphasis should also be on techniques for removing water from hazardous wastes before they are placed in landfills, and on methods for preventing contact of the wastes with water during and after disposal operations. When leachate is eliminated, the problems of monitoring, and subsurface barrier failure and repair can be addressed, and a waste can be effectively isolated. A surface seal landfill design is recommended for maintaining the dry state of solid hazardous wastes and for controlling leachate. Any impervious liner is utilized over the top of the landfill to prevent surface water from seeping into the waste. The surface barrier is also the site where monitoring and maintenance activities are focused. Barrier failure can be detected by visual inspections and any repairs can be made without disturbing the waste. The surface seal landfill does not employ a subsurface barrier. The surface seal landfill successfully addresses each of the four environmental problems listed above, provided that this landfill design is utilized for dry wastes only and is located at a site which provides protection from groundwater and temporary perched water tables. Introduction Although landfills are probably the most com monly used and the oldest methods of hazardous waste disposal, until recently landfill disposal has received relatively little study. Largely because of an increased awareness of environmental effects of anthropogenic activities and the occurrence in the past decade of several hundred damage incidents related to disposal of hazardous wastes (7), there has been an increased interest in identifying sources of hazardous wastes, learning what present disposal practices are, and assessing the adequacy of these procedures. The largest portion of such studies has been sponsored by EPA's Office of Solid Wastes through its general study of reduction, treatment, * Environmental Engineering Division, TRW Inc., 800 Follin Lane, S. E., Vienna, Virginia 22180. Present address: J R B As sociates, Inc., 8400 West Park Drive, McLean, Virginia 22101. and disposal of approximately 600 hazardous wastes (2) and through assessments of hazardous waste generation and disposal in 13 industrial categories. Generally, as more has become known about the need for isolation of hazardous wastes, landfill disposal procedures have been developed to provide for increased waste isolation. Considerable variety still exists, however, among types of land fills used (and the extent of waste isolation achieved) for hazardous waste disposal. This paper summarizes the current status of landfill disposal of hazardous wastes in the United States. The general types of landfills will be defined and will be illustrated by descriptions of several operating hazardous waste landfills. The advan tages, disadvantages, and problems of each landfill will be discussed. The paper will conclude by sum marizing the environmental problems associated with landfill disposal of hazardous wastes and in troducing a suggested landfill system which may solve some of these environmental problems. December 1978 309 General Types of Landfills Although considerable variety exists for hazard ous waste landfills, there is no uniformly used nomenclature in the field. Among the commonly encountered terms are open dump, sanitary landfill, and secure landfill. Definitions for these are pre sented below. Other commonly used terms include: chemical landfill, industrial landfill, hazardous waste landfill, general-purpose landfill, specialpurpose landfill, isolation burial, and environmental containment site. Open Dump As the name implies, an open dump is a disposal site where wastes are piled on the surface of the ground. There are generally no provisions for con trolling vectors, littering due to wind action, or runoff to surface or ground waters. The Resources Conservation and Recovery Act of 1976 specifically prohibits open dumping, and most states also have existing regulations against open dumps. As en forcement becomes more complete, open dumps should be phased out of existence. Sanitary Landfill The sanitary landfill is defined as "a method of disposing of refuse on land without creating nui sances or hazards to public health or safety, by utilizing the principles of engineering to confine the refuse to the smallest practical area, to reduce it to the smallest practical volume, and to cover it with a layer of earth at the conclusion of each day's opera tion, or at such more frequent intervals as may be necessary" (3). Secure Landfill There is no widely accepted definition of a secure landfill. Descriptions of secure landfills (2, 4, 5) vary considerably; however, the following design and operating criteria are generally mentioned in descriptions of secure landfills. The subsurface soil or soil and liner combination has a permeability of less than 10_8cm/sec. The water table is below the lowest level of the landfill. Adequate provisions are made for diversion and control of surface water. Cover material or liners are used, as needed, to suppress air emissions. Provisions are made for leachate collection, for gas venting, as needed, and for monitoring wells. The composition and volume of each waste is known. Incompatible wastes are segregated. Complete records are kept of waste burial. Figure 1 illustrates one possible design for a se cure landfill {4). The use of the term, '`secure," is probably unfortunate because of the implication that a waste deposited in a secure landfill is com pletely isolated for a prolonged period of time. Much additional research is needed to determine how "secure" existing landfills are; indications are that few existing landfills are "secure." Examples of Hazardous Waste Landfills Landfills are used for the ultimate disposal of a wide variety of hazardous wastes. These include petroleum refinery wastes, waste paint sludges and slurries, sludges from industrial wastewater treat ment, and industrial dry process residues. Six operating hazardous waste landfills are described below. Among them are examples of open dumps, sanitary landfills, and "secure" landfills. They not only illustrate the status and variability of hazard ous waste disposal, but also illustrate problems with the use of the above terms. The general features of the landfills are summarized in Table 1. Two land fills are on-site industrial facilities; four landfills ac cept most types of liquid and solid hazardous wastes. Landfill 1: Chromium Sludge Disposal Site This facility is an on-site disposal facility oper ated by a leather tanning and finishing plant. All solid wastes from the plant--leather trimmings, blue trim and shavings, buffing dust, finishing res idues and wastewater screenings, dewatered wastewater treatment sludge--are dumped along the edges of a small ravine in the back of the plant. The hazardous constituents in the wastes include chromium, lead, zinc, copper, and various organic Figure 1. Secure landfill. Data of Farb (4). 310 Environmental Health Perspectives Landfill no. 1 2 3 4 5 6 Table 1. Disposal of hazardous wastes in selected landfills. Type of waste accepted Chromium sludges from leather tanning and finishing Reject batteries and dry battery process residues Hazardous liquid and solid wastes, commingled with municipal refuse Solid hazardous wastes Liquid and solid hazardous wastes Liquid and solid hazardous wastes Location Southeastern U. S. Southeastern U. S. California Northeastern U. S. Southeastern U. S. Northwestern U. S. On-site vs. offsite On-site Off-site Off-site Off-site On-site Off-site Landfill type Open dump Open dump/sanitary Sanitary Secure Secure Landfill Runoff Figure 2. Battery waste disposal site. dyes and pigments. Sources of pollution include surface runoff, leachate to groundwater, and air emissions through wind erosion. Although in 1974 it was estimated that about 90% of the wastes from leather tanning and finishing facilities was disposed of in various types of open dumps (6), the enforce ment of the Resources Conservation and Recovery Act could result in virtual elimination of this prac tice. Landfill 2: Battery Waste Disposal Site The battery landfill shown in Figure 2 is also an open dump. Some engineering practices such as grading, contouring, and compacting have been employed, and small amounts of cover material have been used. The landfill has been operating for over 25 years. Over this period approximately 25,000 tons (23 Gg) of crushed batteries, battery components, cardboard wastes, and mercurycontaminated absorbent resin have been deposited in the landfill. The main hazardous constituents in the waste are mercury, cadmium, lead, and zinc, which comprise approximately 10% of the waste material. Studies of heavy metal migration in the vicinity of the landfill have shown that mercury, lead, cadmium, and zinc have migrated through the soil beneath the site to the bedrock, and, through surface runoff, have contaminated the sediment in a nearby stream. This landfill illustrates one of the important problems in hazardous waste disposal--determining whether migration of any hazardous constituents is acceptable. The company involved has acknowl edged that heavy metals migrate from the site; how ever, they maintain that the rate of migration is slow and that levels are low and are environmentally ac ceptable (7). Landfill 3: Hazardous Liquid and Solid Wastes Commingled With Municipal Refuse The landfill shown in Figure 3 is typical of hazardous waste disposal sites located in Southern California (8), In design and operation, this landfill fits the above definition of a sanitary landfill; how ever, it is also classified as a Class I landfill (similar to a "secure" landfill) in the state of California and therefore accepts a wide variety of hazardous wastes. General design features are as follows. The landfill is located in a blue clay-type soil which has low permeability. The lowest portion of the landfill is at least 10 ft above the water table. The com pleted cells of compacted fill material are sloped in such a way that any leachate from the waste will flow to one point in the landfill where there is a small dike. Any leachate found at this point is col lected and returned to the fill material. Surface water penetration is minimized by daily contouring and covering with compacted blue clay-type soil. The hazardous wastes buried at this facility con sist of a large variety of liquid and solid hazardous wastes. Some of the more common materials are oily wash-out from oil tanks, weak acid solutions, weak alkaline solutions, waste solvents, petro chemical sludges, digested sewage sludges, and similar materials. Figure 4 illustrates the procedure for burial of December 1978 311 Figure 4. Commingling of municipal refuse and hazardous wastes. GROUND SURFACE INTERTABLE Figure 5. Cross-sectional view of solid hazardous waste dis posal landfill located in the northeastern U. S. sion for rainfall to drain away from the wastes quickly. Since the landfill is located in a region with high rainfall, the waste in an active disposal cell is wet much of the time. Therefore, although wastes are solidified prior to being placed in the landfill, the finished waste cell does contain some leachate. It is felt that the surface soil used for final waste cover also allows some water to percolate into the waste, but the amounts are small. Very little information exists upon which to base estimates of leachate quality at this site. The only indication of leachate quality is that when standing water within an active cell is pumped out, tests have sometimes indicated that treatment is needed before the water is discharged. This would lead one to sus pect that any leachate within a finished cell would also require treatment before discharge. If a barrier failure occurred in a finished cell any leachate in the landfill would flow through that point, and the chances of leachate detection by the monitoring wells would be small. Landfill 5: Liquid Hazardous Waste Disposal Site Figure 6 shows a diagram of a landfill which handles a wide variety of liquid and solid wastes from a chemical manufacturing facility (9, 10). The landfill is located on the side of a hill. A 2-ft (0.6 m) layer of compacted clay was used to seal the bottom of the landfill, and a "leaky" earth-holding dike was December 1978 313 Figure 6. Goff Mountain chemical landfill (9). Figure 7. Disposal in concrete silos. constructed at the lower level of the landfill. Liquid and solid wastes are combined in a one to one ratio with soil and placed above the dike. Leachate from the waste runs down the slope to the dike where the water is directed to a holding basin and piped to the wastewater treatment unit. Operating practices in clude waste segregation, continuous blending, and daily coverage. The facility has a projected 20-year 314 life. Types of wastes accepted by the landfill include waste oils and oil sludges (the major waste ma terial), plasticizers, detergents, pitch, tars, poly mers, and inorganic solids such as carbonates and alumina. Occluded metals and toxicants are appar ently impounded in concrete prior to emplacement in the landfill. The primary advantage of this landfill is that the problem of leachate generation is recognized and methods are provided for leachate collection and treatment. Potential problem areas include the clay seal (which probably should have been thicker), structural integrity of the dike, and methods of closing the site after the 20-year period. Landfill 6: Disposal in Concrete Silos The final example of a hazardous waste disposal landfill represents a unique approach to secure landfill design (//, 12). The facility, located in the Northwestern U. S., uses a former missile launch ing site for hazardous waste disposal (Fig. 7). Liquid and solid wastes are placed in under ground structures consisting of a series of silos and vaults. The walls and floors are of reinforced con crete that has been treated with asphalt emulsion on the outside. The silos are approximately 49 m deep with walls 1.8 m thick and floors 4 m thick. Clay and water are also added to absorb the impact of the dropping load and to minimize the potential for fire or explosion. About 95% of the total wastes handled are pesticide wastes, primarily process waste from pesticide manufacturing plants. This disposal method relies on the thickness of the reinforced concrete to isolate the waste from the environment. During active use of some silos and vaults as launching sites, however, sump pumps were required to remove water seeping in through concrete walls. Therefore, leakage of hazardous liquids outwards can occur. No monitoring wells are used. Environmental Problems Associated with Hazardous Waste Landfills The above descriptions show the variety of hazardous waste landfills. Although some are obvi ously better than others, there are common prob lems with which each type of landfill must deal. Many hazardous wastes have a high water con tent which causes a leachate to be generated during compaction and filling activities. Other sources of leachate include rainwater seepage through the waste, and contact with groundwater or perched Environmental Health Perspectives water tables. An important area of research needed is the study of landfill leachate and the determina tion of what concentrations and quantities, if any, of hazardous materials in leachate are environmentally acceptable. The general approach in most landfills is to contain leachate at the site and to prevent its discharge to surface or groundwaters. To retain leachate within the disposal area, sub surface barriers of materials such as concrete, as phalt, butyl rubber, hypalon, vinyl, and clay are used. None of these can seal a landfill indefinitely. For example, asphalt and concrete are sufficiently porous to allow the passage of small quantities of water. An average rate for concrete is 25 pt/yd2/yr (14 l./m2/yr) (National Redi-Mix Concrete Associa tion 1977). Also, cracking is a problem with both asphalt and concrete. Rubber, polyethylene, and vinyl will more effectively prevent leachate from leaving a disposal site; however, the thinness of these materials renders them susceptible to rupture by heavy equipment during disposal operations, and by settling processes after site closure. Monitoring wells are commonly used to detect pollution from landfills. These generally sample the groundwater down-gradient from the landfill. Since groundwater flow is laminar and in one direction, the assumption is that monitoring wells placed in the direction of groundwater flow from the landfill will detect any pollutants. Actually the chances of detecting the pollutants are rather small with even the best monitoring well systems. When a subsurface landfill barrier fails, the leachate enters the groundwater in a concen trated, narrow stream. In the aquifer essentially no mixing occurs, thus the leachate will flow in a very narrow band and may easily miss the monitoring wells. In addition, until the groundwater is reached, leachate from landfills travels vertically through the soil, through cracks, and along the surfaces of any clay seams that may be encountered. This increases the difficulties of correctly placing monitoring wells. The best monitoring system, then, would be one which could be located directly beneath a landfill and would monitor the integrity of the subsurface barrier itself. Monitoring wells are not suitable for this purpose, since their installation would pene trate the barrier itself. One possible monitoring system would detect changes in conductivity (such as that caused by landfill leachate). Once a subsur face barrier has failed, repairs are time-consuming and costly because the waste above the repair site must be removed. Due to the large quantities of wastes involved in most landfills, barrier failure and repair present significant problems. For many years these problems have presented a dilemma to persons involved in landfill disposal of hazardous wastes. The economic advantages and simplicity of landfills make them the disposal tech nique of choice in many instances, yet the problems of leachate, barrier failure, monitoring, and barrier repair remain. The central problem in landfill disposal is leachate control. Recent emphasis has been on de veloping subsurface barriers to contain the wastes and any water. Future emphasis should also be placed on removing water from hazardous wastes to be landfilled and on preventing contact with water during and after disposal operations. When leachate is eliminated, the problems of monitoring, and sub surface barrier failure and repair can be addressed, and a hazardous waste can be effectively isolated. Surface Seal Landfill The surface seal landfill concept was developed in 1976 by the author as a method for landfill dis posal of hazardous wastes which would avoid the problems of leachate migration, and subsurface bar rier failure and repair. Figure 8 illustrates the sur face seal landfill concept. An impervious liner (line AEB in Fig. 8) is utilized over the top of the landfill to prevent surface water from seeping into the waste. The liner would have sufficient width to pre vent lateral water infusion. This surface barrier is also the site where monitoring and maintenance ac tivities are focused. Barrier failure can be detected by visual inspections and any repairs can be made without disturbing the waste. The surface seal land fill shown in Figure 8 does not employ a subsurface barrier, since it serves no useful purpose. Among other advantages of this landfill are simplicity, and low cost. The landfill can also be located in virtually any kind of terrain, i.e., not necessarily in clay, since no leachate will be generated. The landfill will also maintain its integrity even during mild geologi cal disturbances as long as a major shift in the water table does not occur. This technique for land dis posal successfully addresses each of the central en vironmental problems for land disposal stated in the previous sections, provided that this landfill design Figure 8. Lengthwise view of finished landfill cell (13). December 1978 315 is accompanied by land siting which provides pro tection from groundwater and perched water tables. It must be emphasized that only dry wastes can be put in a surface seal landfill. In a recent TRW study of disposal of dry waste from advanced flue gas desulfurization (13), it was concluded that the surface-seal type landfill was the most attractive disposal alternative from both en vironmental and economic aspects. Summary Important aspects of the landfill disposal of hazardous wastes are as follows. There is a great deal of variability in design and operating parame ters such as siting requirements, landfill design, and types of wastes accepted. Among the reasons for this variability are the site-specific nature of landfill disposal, differences of opinion regarding what is environmentally acceptable, variations in state and local regulations, and economic factors. There is no consensus on the degree of waste isolation that is necessary in landfill disposal of hazardous wastes. Because a site-specific evaluation is so important in determining selection of a disposal method and subsequently in determining landfill design and operating procedures, it is difficult to establish (and apply) uniform landfill criteria, although general guidelines can be formulated. Common problems with landfill disposal systems are leachate control, inadequacy of existing monitoring systems, eventual barrier failure, and difficulties in subsurface barrier repair. At the present time, few landfills exist which can assure complete and continued isolation of wastes. The surface-seal landfill shows promise as a simple, economical method for disposal of certain hazard ous wastes. More research and development on landfill dis posal is needed. Some important research areas in clude: leachate reduction techniques, barriers for landfills, detecting landfill barrier failures. REFERENCES 1. Lazar, E. C., Testani, R., and Giles, A. B. The potential for national health and environmental damages from industrial residue disposal. In: Proceedings of the National Conference on Disposal of Residues on Land, Information Transfer, Inc., St. Louis, MO 1976. 2. TRW Inc. Recommended Methods of Reduction, Neutrali zation, Recovery or Disposal of Hazardous Waste, U. S. Environmental Protection Agency, Washington, D. C., 1973. 3. Committee on Sanitary Landfill Practice of the Sanitary En gineering Division. ASCE--Manuals of Engineering Prac tice, No. 39, American Society of Civil Engineers, New York, 1959. 4. Farb, D. Land disposal technology for industrial wastes. In: Management and Disposal of Residues from the Treatment of Industrial Wastewaters, Information Transfer, Inc. Rockville, Maryland, 1975. 5. Slimak, M., et al. Investigation of the consequences of dis posal of lithium organic electrolyte/S02 battery. U. S. Army Electronics Command, Fort Monmouth, New Jersey, 1977. 6. SCS Engineers, Inc. Assessment of Industrial Hazardous Waste Practices--Leather Tanning and Finishing Industry, U. S. Environmental Protection Agency, Washington, D. C., 1976. 7. Versar, Inc. Unpublished report. Heavy metal migration on industrial battery landfill disposal site, Springfield, VA 1974. 8. Versar, Inc. Assessment of Industrial Hazardous Waste Practices, Inorganic Chemical Industry. U. S. Environ mental Protection Agency, Washington, D. C., 1975. 9. Slover, E. E. Solid waste disposal in a multi-product chemi cals plant. In: Symposium Proceedings: The Textile Industry and the Environment, American Association of Textile Chemists and Colorists, Washington, D. C., 1973. 10. Slover, E. E., and Hall, M. E. Use of biological solids in chemical landfill operation. In: Management and Disposal of Residues from the Treatment of Industrial Wastewaters, Information Transfer, Inc., Rockville, Maryland, 1975. 11. TRW Systems Group. A Study of Selected Landfills Desig nated as Pesticide Disposal Sites, U. S. Environmental Protection Agency, Washington, D. C., 1975. 12. Ghassemi, M., Quinlivan, S. C., and Day, H. R. Landfills for pesticide waste disposal. Environ. Sci. Technol. 10 (13): 1213 (1976). 13. TRW Inc. Evaluation of Dry Sorbents and Fabric Filtration for FGD. U. S. Environmental Protection Agency, Washington, D. C., 1977. 316 Environmental Health Perspectives